How much energy (kJ) is required to convert a 76.4 g acetone (MM = 58.08 g/mol) as a liquid at -30°C to a solid at -115.0°C?

• A. -11.406 kJ
• B. -39.820 kJ
• C. -22.811 kJ
• D. -82.592 kJ

Answer: (C)

Verified step by step guidance

1. Calculate the energy required to cool the liquid acetone from -30°C to its melting point at -95°C using the formula: q = m * C * ΔT, where m is the mass, C is the specific heat of the liquid, and ΔT is the change in temperature.
2. Convert the mass of acetone from grams to moles using its molar mass: moles = mass / molar mass.
3. Calculate the energy required for the phase change from liquid to solid at the melting point using the formula: q = n * ΔH_fusion, where n is the number of moles and ΔH_fusion is the enthalpy of fusion.
4. Calculate the energy required to cool the solid acetone from its melting point at -95°C to -115°C using the formula: q = m * C * ΔT, where C is the specific heat of the solid.
5. Sum the energies calculated in the previous steps to find the total energy required for the entire process.